Inorganic staple fiber including glass fiber, ceramic fiber and mineral fiber like mineral, glass or slag wool have been used extensively for reinforcing numerous materials and for enhancing the fire resistance of products. For example, glass fiber has been used to reinforce and enhance the fire resistance and rating of gypsum board.
At least two processes are typically used for adding glass fiber in the manufacture of gypsum board. The first process feeds dried glass fiber having a low moisture content and a chemical sizing on the fiber into wetted calined gypsum, usually while the wetted material is being mixed and transported in an auger mixer. The fiber is dispersed in the mix by the mixing action. The second process involves adding the fiber directly into the water to make a slurry for a gypsum board before other ingredients are added. The water is typically a low quality, such as tap water, well water, lake or river water, i. e. plant water. The second process using low quality water is preferred by some manufacturers. For the second process, it is necessary that the fiber disperse quickly and uniformly. If it doesn't, each cubic inch of the board won't have enough fibers to pass the fire test and excess fiber will have to be used to insure enough fibers are in each portion of the board.
Unfortunately, the low moisture fiber made for feeding into the wetted gypsum mixture does not disperse uniformly and quickly necessitating that excess dry fiber be used or that a dispersant be added to the water prior to adding the fiber. Some dispersants found to work marginally in dispersing the dry fiber are flammable, presenting an undesirable risk to the manufacturing plants using the fiber.
Other glass fiber products are available in both dried and having a higher moisture content, both with a chemical sizing thereon depending on the intended application. Almost all glass fibers have a chemical sizing on their surface to protect the surface from abrasion and scratches during manufacture and use which will substantially reduce the strength of the fiber. The chemical sizing also can function to aid dispersion and to provide a better bond between the glass fiber and a matrix that the fiber will reinforce, such as a plastic material, a resin binder, etc.
Dry glass fiber products intended for use in plastics products will not disperse sufficiently in water and therefore are not suitable. Various wet chop fiber products, i. e. undried, chopped continuous glass fiber for use in making nonwoven mats in wet process machines or paper machines also did not disperse sufficiently. The sizing on these latter fiber products is designed to cause the fiber to disperse well in a "whitewater" and to bond well to a urea formaldehyde or acrylic resin binder and apparently for that reason do not separate well in plain water, i. e. water without one or more dispersants added. Whitewater used in wet process machines for making mats, unlike plain water in the gypsum board slurry process, contain various viscosity modifiers, defoaming agents, dispersants and other chemical additives that permit the fibers to disperse as desired.
Therefore, there is a need for a fiber product having a chemical sizing thereon that will permit the fiber to disperse quickly, adequately and uniformly in plant water.